Impregnation of leather and products thereof



Patented Oct. .29, 1940 IMPREGNATION OF LEATHER AND PRODUCTS THEREOFNorman N. Gay, Berkeley, Calii'., assignor to Standard Oil Company ofCalifornia, San Francisco, Calif., a corporation of Delaware 'NoDrawing.

7 Claims.

My invention pertains to the preservation and treatment of leather byimpregnating leather with a polymer obtained by the polymerization of amixture of both normal and iso-butene, and articles of manufacture andleather impregnating compositions containing such polymers.

All natural fat and oil must be removed from hide prior to tanning topermit penetration of the tanning liquors. Dried, tanned leather isstiff because the natural lubricant has been removed and the fibrebundles fail to slide against and between each other. Leather in thiscondition deteriorates rapidly if the leather is repeatedly bent orflexed because the frictionof the individual fibres causes internalwear. A lubricant and preservative must be added to leather before it isused, to replace the natural fat and oil removed prior to tanning, andto prevent deterioration caused by internal wear.

Various compositions-have been used for this purpose, among which areneats-foot oil, fish oil and castor oil. The best oils soften andpreserve leather, and do not become rancid or, greasy and discolor theleather. g 5

The use of the polymer described and claimed herein has been found tohave numerous advan tages. When properly prepared it is water white andhence does not discolor leather. It is highly stable and, therefore,does not become rancid.

By reason of the fact that it does not hydrolyze tion step is omittedthe odor and taste of the polymer is slight. A most important feature ofthe polymer is that it is normally liquid, even at temperatures as lowas F., and, thus, may be used directly as a preservative without the useof any solvent or emulsifying agent. In this it has great advantage oversolids, such as isobutene polymers, used as leather preservatives.

The polymer is soluble in mineral oils and in most other substances withwhich leather is impregnated.

The polymer described and claimed herein as a leather preservative isderived from the polymerization of a mixture of normal and iso-butene,

the ratio of normal butene to iso-butene being substantial, undercircumstances such that both the normal and the iso-butenes arepolymerized.

Appropriate sources of such oleflnes, are gases Application February 6,1939, Serial No. 254,801

obtained from thermal cracking of petroleum, crude oil, distillates orresiduums.

Sulfur compounds in the charging stock such as hydrogen sulfides and lowboiling mercaptans are preferably removed prior to polymerization. Thesemay be removed by use of an aqueousalkaline hydroxide such as sodiumhydroxide to form water soluble products, or by use of sodium plumbiteand the conventional'doctor treatment.

The sulfur free olefinic material is dried, cooled and then polymerizedin either gaseous or liquid phase, the latter being preferred, with theaid of a polymerization catalyst, usually anhydrous aluminum chloride.The reaction temperature is preferably at approximately atmospheric.However, lower and higher temperatures, below F., have been foundsatisfactory. If gaseous phase polymerization is used, the gas may'bebubbled through a suspension of anhydrous aluminum chloride in petroleumether.

The removal of aluminum chloride sludge may be accomplished bysettlement, filtration through a rock filter, followed by claytreatment.

The polymers may then be separated from the accompanying unpolymerizedlower boiling point hydrocarbons, such as butane, by any ordinaryvaporization process, and the polymers themselves may be-segregated intovarious cuts or fractions according to viscosity or volatility desiredby ordinary processes of distillation with fractionation. Theunpolymerizednormal and isobutene, together with accompanying lowerboiling point hydrocarbons, may be recycled for the polymerization ofthe unpolymerized normal and iso-butene.

The entire polymer product may be subjected to a saturating,non-destructive hydrogenation at super-atmospheric temperature andpressure in the presence of a hydrogenating catalyst such as finelydivided catalytic nickel.

The percentage of polymerized iso-butene in the finalproduct of thepolymerization step has an important effect on the viscosity of thebuteneiso-butene polymer. of iso-butene polymers in the finished productthe higher the viscosity of the finished product. Table 1 belowillustrates such efiect:

. Table 1 Percent of iso-butene polymers...

Viscosity at 210 F. (S. S. U

The higher the percentage zation temperature, since normal butenepolymerizes scarcely at all below 0 while isobutene will polymerizequite readily at 0 F. and below. Thus by keeping the polymerizationtemperature within the desired proximity to 0 F.. the percentages ofnormal and iso-butene polymerized can be controlled.

The percentage of normal to iso-butene present in the charging stockdoes not seem to be important. The important factor is the percentagesof such constituents present which are in fact polymerized. If thetemperature rises above 0 F. for any appreciable time the normal butenespolymerize rapidly enough so that their proportion of the finishedmixture is substantial. Table 2 below is illustrative of resultsobtained by the polymerization of a mixture of normal and isobutene ina. continuous system:

Table 2 Run Percent of normal butene in charging stock 26. l 27. 2 27. 629. 1 Percent iso-butenc in charging stock. 13. 5 12.6 13. 7 12. 8Percent normal butene in recycle stock. 15. 5 17. 7 18. 0 16. 9 Percentiso-butcnein recycle stock 3. 9 4. 0 4. 7 4. 0 Percent polymers fromnormal butene. 48.0 49. 2 49. 2 56. 0 Percent polymers from iso-butene40. 5 .41. 5 4i. 3 39. 0 Volumes of liquid charging stock per volume ofcatalyst per hour 0.8 0. 7 0.6 1.4 Recycle ratio, volume of recyclestock per volume of fresh stock 2. 5 2. 6 2. 7 2. 7 Temperature, F., in33 -40 35 24 Temperature, F., out +57 +42 +44 +25 Average temperature ofpolymerization,

F 12 1 4 0 Viscosity at 210 F. (S. S. U.) 76 213 135 226 Percentconversion, normal butene 61 54 64 Percent conversion, lso-butene lCO 9992 95 Inorder to produce a viscous, liquid polymer it is necessary thatthe charging stock contain both normal and iso-butene and that both bepolymerized in substantial portions. The polymer described herein mustbe distinguished from the Among the fractions from such polymerizedmixtures ot normal and iso-butene used successfully for treatingleather, is a fraction having the following characteristicsr I Gravity,A. P. I? 31.8 Flash I s50 Viscosity, S. S. U. at F 4782 Viscosity, S.8.11. at 210 F 213 Color, A. s. 'r. M 1.5

The method of impregnating leather as described and claimed herein hasbeen found valuable not only for the more common uses of leather, buthas been found especially valuable for the impregnation of leather gasmeter diaphragms. Such diaphragms must, for accuracy, remain flexiblefor long periods under conditions whichtend rapidly to harden leather.Ordinary leather preservatives of sufilciently high viscosity are notsatisfactory for such purpose.

The description given above is merely illustrative. Numerous" variationsof manufacture and use may be made within the scope of the appendedclaims.

I claim:

1. The method of treating leather, which comprises impregnating theleather with a polymer obtained by polymerization oi a mixture of bothnormal and iso-butene.

2. The method according to claim 1 in which the polymer is normallyliquid.

3. The method according to claim 1 in which the polymer is of amolecular weight from 200 to 780.

4. The method of treating leather which comprises impregnating theleather with a normally liquid polymer of a mixture of both normal andiso-butene, said polymer having a molecular weight less than 780 andmore than 200.

5. An article of manufacture comprising a leather, having incorporatedtherein a normally liquid polymer of a. mixture of both normal andiso-butene.

6. An article of manufacture comprising a leather having incorporatedtherein a normally liquid polymer of a mixture of both normal andiso-butene, said polymer having a molecular weight less than 780 andmore than 200.

7. A leather impregnating composition having the quality of keepingleather soft and flexible without being sticky and being substantiallynonvolatile and capable of being used as a leather dressing withoutadmixture with any other substance comprising a normally liquid polymerof a mixture of both normal and iso-butene and having a molecularweightless than 780 and more than 200.

NORMAN N. GAY.

